Harold (Hal) and Herbert (Herbie) were the first set of twins to reach number one in the UK as a duo,[2] followed years later by The Proclaimers. They were supported by Cliff Richard on their only UK tour. Their second single, "Forget Me Not," reached Number 12 in the US Billboard chart later in 1958. After two further low-ranking entries in 1959, they never reached the charts again.

Eventually, disillusioned with diminishing returns, the brothers returned to their day jobs, with each pursuing college degrees. They did not perform again until 1977, when a mutual friend booked them to appear at his new nightclub. Sometimes they performed with their younger sibling, Jack, and thus appeared as the Kalin Brothers.

They disappeared again as a performing act, until 1989. Then, their one-time support act, Cliff Richard, invited them to play at his Wembley Stadium 'The Event' concerts, as part of a sequence paying homage to the 1950s television pop show, Oh Boy!